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Arnica montana is commonly used in herbal ointments and oils applied on the skin as an anti-inflammatory and pain-relieving agent for aches, bruises, and sprains on unbroken skin. Highly diluted homeopathic preparations are considered safe and are widely used for the treatment of injuries. However, full doses of arnica may be toxic when taken by mouth. Arnica may also be damaging to the heart, resulting in high blood pressure.

The U.S. Food and Drug Administration (FDA) has declared arnica an unsafe herb due to adverse effects reported when taken by mouth. In contrast, the German market offers over 100 preparations of arnica to its consumers. In Canada, arnica is not allowed for use as a non-medicinal ingredient for oral (by mouth) use products.

Note: This monograph does not include Heterotheca incloides (Mexican arnica).

evidence table

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Bruising
(Grade: C)
Homeopathic and topical (on the skin) arnica is widely used to prevent or treat hemorrhages (heavy bleeding), hematomas (blood clots), and bruising. More study is needed in this area to draw a firm conclusion.

Coagulation (blood clotting)
(Grade: C)
Homeopathic arnica does not seem to affect bleeding time or platelet count. More studies are needed in this area.

Diabetic retinopathy
(Grade: C)
Homeopathic arnica has been used for improving retinal microcirculation, thereby slowing the progression of damage to the retina of the eye in diabetics. Although early study is promising, additional study is needed before a firm conclusion can be reached.

Diarrhea in children (acute)
(Grade: C)
Arnica has not been well studied for its effects on diarrhea, but early study suggests that homeopathic arnica may decrease the duration of diarrhea in children. Further study is needed to make a strong recommendation.

Ileus (postoperative)
(Grade: C)
Postoperative ileus is characterized by a temporary impairment of gastrointestinal motility. Symptoms may include abdominal pain, nausea and vomiting, reduced desire to eat, and an inability to pass gas or stool. There is early evidence that homeopathic arnica treatment may reduce the duration of ileus after abdominal or gynecologic surgery. Well-designed research is needed to make a strong recommendation.

Osteoarthritis
(Grade: C)
Arnica gel has been used on the skin for osteoarthritis pain and stiffness, due to its anti-inflammatory constituents. Although early study is promising, additional study is needed.

Pain (post-operative)
(Grade: C)
Some patients use homeopathic arnica to relieve pain after an operation. However, arnica is often used with other pain-relieving agents. It is unclear how effective arnica is alone for the treatment of pain.

Stroke
(Grade: C)
Homeopathic arnica has been used in stroke recovery. More research is needed before a firm recommendation can be made.

Trauma
(Grade: C)
Many patients use arnica to relieve pain postoperatively. Further study is needed to define the effectiveness of arnica in postoperative pain.

Muscle soreness
(Grade: D)
Homeopaths believe that arnica may be effective in relieving pain due to delayed onset muscle soreness, which is defined by exercise to which subjects are unaccustomed. Currently, it is not recommended to give arnica for this indication, although it does not appear to be unsafe for use.

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